1. Field of the invention
The present invention relates to a video signal recording and reproducing apparatus for recording and reproducing video and audio signal, and more particularly to a video signal recording and reproducing apparatus suited for editing the video signal or audio signal or both.
2. Description of the Prior Art The video tape recorder (VTR, hereinafter) having an editing function accompanying operational processing of a recorded signal in desired such as, for example, fading-in and fading-out of the video signal or audio signal. To realize such an editing function, a method is known that reproduces a recorded signal, carries out specified signal processing of the reproduced signal, and records the processed signal in the area where the reproduced signal has been recorded on the recording medium. For example, in the recording and reproducing apparatus disclosed in Japanese Laid-Open Patent Application No. 60-223007 or No. 2-76102, in order to reproduce a track located a specific time in advance of the track traced by a recording head (prior reproduction), a prior reproduction head is disposed in addition to the recording head on a rotary cylinder.
In a conventional constitution, editing of a digitally recorded signal accompanying the operational processing, such as fade-in and fade-out, requires reproduction signal processing such as error detection and correction of the reproduced data prior to recording, the above-mentioned operational processing, and recording signal processing such as error correction code addition to the signal after the operational processing. Further, if the recorded signal is compression coded video signal or audio signal, decoding of the reproduction signal and compression coding of the signal after the operational processing are required.
These additional signal processings are complicated and increase the hardware scale. Further, the quantity of data to be reproduced by the prior reproduction must be increased with the increase of the time required for such signal processing. The greater the prior reproduction quantity, the larger becomes the difference between the mounting heights of the recording head and the prior reproduction head in the VTR having helical scan recording type with a rotary head cylinder. Considering the VTR for recording wide-band signals such as High Definition TV signals, having a large number of tracks per frame the difference in the mounting heights of the prior reproduction head and recording head is required to be about several millimeters, and each head must be mounted at a precision of several microns or less. If there is an error in head mounting, while the prior reproduction head is on the track to be reproduced, the recording head may be off the track to be recorded, and precise editing cannot be expected.
In a method disclosed in Japanese Laid-Open Patent Application No. 1-152877, the principal information composed of video signal or audio signal is recorded in a state without being faded, and a fade control signal is recorded as the duty of the rotary head phase control signal. In reproduction, the output level is controlled by using the fade control signal. In this method, fade-out and fade-in editing without prior reproduction is possible. However, in order to rewrite the fade control signal, the rotary head phase control signal also must be rewritten. If the timing of the control signal is deviated from its original timing, the tracking varies. Therefore, in order to obtain a stable reproduction image, a signal of the same timing as before rewriting must be recorded at an extremely high precision.